Specifications

ESS Technology, Inc. SAM0025A-062397 87
ES1879 DATA SHEET
POWER MANAGEMENT
PRELIMINARY
POWER MANAGEMENT
Power management in the ES1879 is controlled by PnP
Configuration register 2Dh. In previous
Audio
Drive
®
chips,
power management was controlled by I/O port
Audio_Base+7h. Only bit 5 (FM reset) and bit 7 (suspend
request) of I/O port Audio_Base+7h are supported in the
ES1879.
GPO, XSD, and XSC are not affected during power-down.
XA[3:0] are high-impedance during power-down Modes 0
and 1.
Power Mana
g
ement Characteristics
The ES1879 has four power modes. The mode is
determined by bits 1 and 0 of Vendor-Defined Card-Level
register 2Dh.
In any mode, the configuration device can always be read
and written.
Mode Transitions
The mode can be changed at any time with only one
restriction: if a crystal is connected to XI/XO, and the chip
is in mode 0, then the chip must be placed in mode 1 for a
period of 25 milliseconds or more to allow the oscillator to
settle, before changing to mode 2 or mode 3.
BIOS Power Mana
g
ement
There are at least three types of BIOS power
management:
1. Suspend-to-Disk. Here the context of the ES1879 is
uploaded to disk, then power is removed from the
ES1879. Later, power is applied to the ES1879 along
with a hardware reset, and the context of the chip is
downloaded.
2. Idle power-down. The microcontroller is stopped or
slowed. Application software is not running. The
ES1879 is put in full power-down mode by BIOS. The
power supply is still connected to the chip. Later, the
BIOS returns the ES1879 to full power up.
3. Power reduction. If the system can generate an
System Management Interrupt (SMI) upon I/O access
to the audio and FM addresses, then the BIOS can
implement a power reduction technique: the BIOS
periodically polls the activity flags of the ES1879 in
order to determine if the chip is in use. If not in use for
some period, it can power down the chip and enable
the SMI. The first application to access the audio or FM
address space will trigger the SMI, which causes the
BIOS to power up the ES1879, and deactivate the SMI.
BIOS power management is well suited to a DOS
environment. It must also work with the ES1879 Windows
driver which implements power management as well.
Suspend-to-Disk / Resume-from-Disk
Suspend-to-Disk is the name given to the procedure
where the entire context of the ES1879 is uploaded to be
saved on disk. After saving the context, power can be
removed entirely from the ES1879. When power is re-
applied (and a hardware reset is given), the ES1879 state
must be restored from the saved context.
The suspend procedure consists of the following tasks:
1. Upload PnP configuration information.
2. Upload FM registers.
3. Upload mixer registers.
4. Upload MPU-401 state.
5. Upload audio state (using suspend request: bit 7 of
port "Audio_Base+7h").
An example DOS assembly language program is available
demonstrating suspend-to-disk, followed by resume-from-
disk, from a TSR that hooks the system timer interrupt.
This program demonstrates how a DOS application such
as a game can be suspended in the middle of audio
playback.
DMA and Interrupts During Suspend-to-Disk
The ES1879 cannot properly suspend and resume during
audio playback unless the DMA and interrupt controller
are also properly suspended. Alternatively, the DMA and
interrupt controllers should not have power removed. In
the latter case, it is important that all DRQ and IRQ lines
are held low. All bus lines should be low if power is
removed from a device connected to the bus that has its
power supply removed. Also, during and after reset, the
Table 29 Power Mode Description
Mode Description Notes
0 Full power-down. Crystal oscillator dis-
abled. AOUT_L/R held at approximately
CMR by high value resistors.
All inputs
static at
VDDD or
GND.
1 Crystal oscillator enabled. Analog pow-
ered down.
All inputs
other than
XI are
static.
2 Analog powered up. ES978 interface
up. Joystick, MPU-401 up. I
2
S up.
Audio, FM, ES689/ES690 interface, and
DSP serial interface down.
Digital
standby.
3 Full power on. This is the state after
hardware reset.
Normal
operating
conditions.